The present invention relates to a diagnostic method and apparatus for clamping the blood glucose concentration of a subject at any one of a plurality of levels.
The glucose clamping technique has been envisioned as a valuable diagnostic tool for the early identification of derangements in glucose metabolism in human beings. During glucose clamping, the normal glucose insulin relationship is interrupted by placing the patient's blood glucose concentration under the investigator's control. Thus, by clamping a patient's blood glucose concentration at a hyperglycemic level, with no additional exogenous insulin, the pancreatic beta cell response to glucose may be observed. Likewise, by holding the patient's blood glucose concentration at a normoglycemic level, with programmed insulin infusion and feedback controlled infusion of dextrose, the sensitivity of body tissues to insulin may be studied.
The diagnostic technique of glucose clamping therefore differs from the aim of therapeutic techniques of glucose monitoring systems such as that disclosed in U.S. Pat. No. 4,151,845 since such systems act as a life support system and aid in the body's inability to maintain a normoglycemic level.
The glucose clamping technique also differs from oral glucose and insulin tolerance tests since the hyperglycemic clamp, unlike the oral glucose tolerance test permits the time course of glucose metabolism by the body to be quantified and separated into the early and late phases of insulin secretion. The normoglycemic clamp with insulin infusion, eliminates the possible danger of hypoglycemic excursions present with insulin tolerance tests. The complex physiological responses to hypoglycemia are also avoided, thus providing a more reliable estimate of tissue sensitivity to insulin.
While the glucose clamping technique has been recognized as a potentially valuable diagnostic tool, no automatic method or system for utilizing same has been reliably carried out.
While various algorithms have been utilized for carrying out such a technique, these have not been sufficiently reliable to achieve the desired results of an automatic method and apparatus for glucose clamping.